Some of various electronic apparatuses use a connector for inserting and connecting a flexible printed circuit board. For example, the connector is mounted on a surface of a circuit board and the flexible printed circuit board is inserted and connected to the connector. Consequently, the circuit board and the flexible printed circuit board are connected to each other through the connector. Such a connector is disclosed in Patent Document 1, for example.
Referring to a connector for connecting a flexible printed circuit board, a connecting terminal 11 for a connector shown in FIG. 1 is inserted into a terminal inserting hole provided in a housing thereof, and a plurality of connecting terminals 11 for a connector is arranged at a certain pitch. The connecting terminal 11 for a connector has such a shape that a fixed piece 14 and a movable piece 15 which are disposed in almost parallel with each other are coupled to each other through a coupling portion 16 which is almost perpendicular to both of the pieces 14 and 15. A lower surface of a tip portion of the fixed piece 14 is exposed from a bottom face of the housing. When the connector is to be mounted on the circuit board, the lower surface of the tip portion of the fixed piece 14 is bonded to an electrode pad 12 of the circuit board through a solder as shown in FIG. 2(A). A movable contact 17 is provided on the lower surface of the tip portion of the movable piece 15, and a rear end of the movable piece 15 serves as an operation receiving portion 18 for tilting the movable piece 15 like a lever by means of a cam portion.
In a flexible printed circuit board 19, as shown in FIG. 3, a lead wire 21 is formed on a surface of a resin sheet 20 and a wide contact portion 22 is provided on a tip of the wiring lead wire 21 to be connected to the connecting terminal 11 for a connector.
An end of the flexible printed circuit board 19 is inserted between the movable piece 15 and the fixed piece 14 in the connecting terminal 11 for a connector which are arranged in a line, and each contact portion 22 of the flexible printed circuit board 19 is aligned with each movable contact 17. As shown in FIG. 4, when the operation receiving portion 18 of the connecting terminal 11 for a connector is pushed up by means of the cam portion in that state, the movable piece 15 is tilted so that the movable contact 17 is moved downward and the movable contact 17 comes in pressure contact with the contact portion 22, and furthermore, the flexible printed circuit board 19 is caused to mate into a portion between the movable contact 17 and the fixed piece 14 to connect the flexible printed circuit board 19 to the connector.
When the number of the terminals of the connector is increased, however, an array pitch of the connecting terminal 11 for the connector is shortened. When a refining technique for the flexible printed circuit board progresses, moreover, the array pitch of the contact portion 22 can be shortened more greatly. More specifically, in case of the flexible printed circuit board 19 fabricated by a subtractive process, minimum pattern dimensions Wa and Wb shown in FIG. 3 are 50 μm, a minimum space dimension Sa is also 50 μm, and a tolerance is ±20 μm. In a minimum pitch design, moreover, a width Wc of the contact portion 22 is 100 μm and a space Sb between the contact portions 22 is 100 μm. In consideration of the tolerance of ±20 μm, a width has a variation within a range of 80 μm to 120 μm in the contact portion 22 of the width Wc=100 μm. In order to reliably cause the connecting terminal 11 for the connector to come in contact with the contact portion 22, accordingly, it is necessary to set the width of the connecting terminal 11 for the connector to be equal to or smaller than 80 μm.
In the case in which the connecting terminal 11 for the connector which has a small width is used, thus, the array pitch of the connecting terminal 11 for the connector is also reduced correspondingly. In the case in which the connecting terminal 11 for the connector is soldered to the electrode pad 12, however, a spread of the solder 13 in the electrode pad 12 (the circuit board) is greater than the width of the connecting terminal 11 for the connector. For this reason, in the case in which the connecting terminal 11 for the connector is arranged in a small array pitch, there is a fear that the solder 12 might spread over the adjacent electrode pad 12 to short-circuit the connecting terminals 11 for the connector as shown in FIG. 2B. In particular, a positional shift of the connecting terminal 11 for the connector or an excessive amount of supply of a solder increases the fear that the connecting terminals 11 for the connector might be short-circuited.
In order to reduce the spread of the solder 13, thereby preventing the short circuit between the connecting terminals 11 for the connector which are adjacent to each other, it is effective to decrease the width of the connecting terminal 11 for the connector. In order to raise a contact pressure at which the movable contact 17 of the connecting terminal 11 for the connector comes in contact with the contact portion 22, moreover, it is effective to decrease the width of the connecting terminal 11 for the connector, thereby reducing an area of the movable contact 17.
However, a spring property or a rigidity of the connecting terminal 11 for the connector is deteriorated when the width of the connecting terminal 11 for the connector is decreased. To the contrary, there is caused a drawback that the contact pressure of the connecting terminal 11 for the connector and the contact portion 22 is reduced or a force for holding the flexible printed circuit board 19 by the connecting terminal 11 for the connector is reduced.